1. Field of the Invention
The present invention relates to a printer and a printing method that decurl a recording medium.
2. Description of the Related Art
A printer that prints data onto a roll recording medium includes a decurling mechanism that decurls a recording medium. The decurling mechanism decurls the recording medium to inversely curl the recording medium by moving and pressing a raised member to the recording medium or pressing the recording medium to the raised member.
However, when the raised member keeps in contact with the same portion of the recording medium for a longtime, a crease is produced at the portion. Since there is a high possibility that ink does not normally adhere to the portion of the crease production, a problem of deterioration in print quality can arise. Japanese Patent Publication No. 3190489 discusses an apparatus that solves the problem. A decurling apparatus discussed in Japanese Patent Publication No. 3190489 includes a mechanism driven with power of a roller that conveys a recording sheet. When the roller rotates in the winding direction of the recording sheet, the mechanism has a decurling function, and when the roller rotates (inversely rotates) in the rewinding direction of the recording sheet, the mechanism moves to a specific position, thereby cancelling the decurling.
Japanese Patent Application Laid-Open No. 2002-104688 discusses a recording apparatus having a function of preventing the aging deformation of a recording sheet. It is assumed that printing is performed in the recording apparatus while the recording sheet passes through space between a grip roller having a large number of projections on the surface thereof and a pinch roller. Before the printing, a contact portion of the recording medium with the grip roller changes as predetermined time passes.
In printing on a roll recording medium with a dye-sublimation printer as a thermal transfer printer, heat generated by a thermal head is advantageous to decurl the recording medium. In this case, as the number of print colors (number of inks) increases, the heating time of the recording medium is prolonged. Therefore, by actively pressing the portion heated by the thermal head to the raised member, excessive decurling can produce a crease at the portion. If the crease is made in a print area (area in which a large part of an image is printed) on the recording medium, a problem of deterioration in print quality can occur.
The problems can be solved by additionally installing the mechanism discussed in Japanese Patent Publication No. 3190489 in the printer because the mechanism has a function of cancelling the decurling. However, to add the mechanism, the installing space of the mechanism needs to be secured, and the size of printer therefore increases and product costs rise. Since it is assumed that the recording apparatus discussed in Japanese Patent Application Laid-Open No. 2002-104688 records data on an unroll recording medium, the problems are not solved only by periodically changing the contact position between the recording medium and the grip roller.